Double transformer balun for maximum power amplifier power

ABSTRACT

Double transformer balun for maximum PA (Power Amplifier) power. A novel approach is presented herein by which conversion from a differential signal to single-ended signal may be achieved using a double transformer balun design. The secondary coils of the double transformer balun also operate as a choke for the PA supply voltage. The secondary coils can operate as an RF (Radio Frequency) trap or choke to keep any AC (Alternating Current) signal components and to pass any DC (Direct Current) components. By using a double transformer balun design, relatively thinner tracks may be employed thereby ensuring a high degree of electromagnetic coupling efficiency and high performance. Also, these relatively thinner tracks consume a relatively small amount of space on the die. The double transformer balun design also includes a matching Z (impedance) block that is operable to match the Z of an antenna or line that the PA is driving.

CROSS REFERENCE TO RELATED PATENTS/PATENT APPLICATIONS ContinuationPriority Claim, 35 U.S.C. §120

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120, as a continuation, to the following U.S. Utility patentapplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility patent applicationfor all purposes:

1. U.S. Utility patent application Ser. No. 10/819,388, entitled “Doubletransformer balun for maximum power amplifier power,” (Attorney DocketNo. BP3115), filed Apr. 7, 2004, pending, and scheduled to be issued asU.S. Pat. No. 7,904,108 on Mar. 8, 2011 (as indicated in an ISSUENOTIFICATION mailed on Feb. 16, 2011), which claims priority pursuant to35 U.S.C. §119(e) to the following U.S. Provisional Patent Applicationwhich is hereby incorporated herein by reference in its entirety andmade part of the present U.S. Utility patent application for allpurposes:

-   -   a. U.S. Provisional Patent Application Ser. No. 60/554,573,        entitled “Double transformer balun for maximum power amplifier        power,” (Attorney Docket No. BP3115), filed Mar. 19, 2004, now        expired.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates generally to communication devices; and, moreparticularly, it relates to connectivity of the various components andcircuits within such communication devices.

2. Description of Related Art

Data communication systems have been under continual development formany years. Within such communication systems, there are manycommunication devices included therein that that include variousintegrated circuits, chips, modules, and functional blocks. Thesecommunication devices may be transceivers, transmitters, receivers, oreven other peripheral type devices. Within these communication devices,various chips (e.g., sometimes referred to as integrated circuits,packages, encapsulated chips, and so on) are typically mounted on a PCB(Printer Circuit Board) and are typically communicatively coupled viathe PCB to other chips that are mounted thereon. The manner in thesevarious chips communicatively couple to the PCB can introduce someserious deficiencies to the overall communication device's performance.Moreover, even within the actual chips within these communicationdevices, the manner in which the various circuitry portions therein arecommunicatively coupled to one another may also introduce seriousdeficiencies to the overall communication device's performance. In manyinstances, differential type signals are employed within suchcommunication devices for performance considerations such as noiseimmunity. As such, there is oftentimes a need to perform transformationsto and from differential signals and single-ended signals. That is tosay, there is often a need to transform a signal from a differentialsignal type to a single-ended signal type and vice versa. To performthis conversion from a signal from a differential signal type to asingle-ended signal type, the circuitry of the communication device willtypically employ a balun (i.e., a balanced/unbalanced transformer). Thatis to say, within an integrated circuit, a communication approach bywhich this transformation (e.g., differential to single-ended) isperformed is to use a balun within the circuitry of a chip. The balun istypically implemented as a transformer on the chip whose windings areactually implemented on the die of the chip.

Until very recently, these baluns were implemented as being off-chip,i.e., on the PCB (Printer Circuit Board), and they were typicallyimplemented in the form of micro-strip lines. More recent attempts tointegrate a balun onto a chip have met with some serious performancelimitations. For example, parallel winding, inter-wound winding, overlaywinding, single planar, square wave winding, and concentrical spiralwinding on-chip baluns have been tried with limited success. Each ofthese on-chip baluns suffers from one or more of: low quality factor,(which causes the balun to have a relatively large noise figure); toolow of a coupling coefficient (which results in the inductance value ofthe balun not significantly dominating the parasitic capacitance makingimpedance matching more complex); asymmetrical geometry (which resultsin degradation of differential signals); and a relatively high impedanceground connection at the operating frequency.

Moreover, in the wireless communication system context (e.g., RF (RadioFrequency) communication systems), these integrated circuits have metwith limited success larger in part to the manner in which they areimplemented. In addition, within higher power applications, the size ofthe balun on the die can itself introduce some significant problems.This is largely because the size of the tracks of the transformed balunto support these higher power applications is implemented usingrelatively wider tracks and this inherently requires a larger spatialarea on the die.

FIG. 1A is a diagram illustrating a prior art embodiment of a singletransformer balun (having relatively wide tracks) within an integratedcircuit (shown using a side view). As shown in this embodiment, a chip(e.g., which may alternatively be referred to as an encapsulated chip,package, an integrated circuit, or other terminology) typically includesa die (e.g., a silicon substrate) on which a certain amount of circuitryis emplaced. This circuitry may be referred to as on substratecircuitry. One portion of the on substrate circuitry may be a singletransformer balun that is implemented as a transformer as describedabove. To support higher power applications, such a single transformerbalun may be implemented using wound tracks on the substrate. Thewindings (shown as a winding 1 and a winding 2) are separated by adielectric insulating layer, and the magnetic coupling between thewindings operates as a transformer.

FIG. 1B is a diagram illustrating the same prior art embodiment of asingle transformer balun (having relatively wide tracks) within anintegrated circuit (shown using a top view). This embodiment shows aside view of the very same components as within the previous diagram. Ascan be seen, a chip may have several (sometimes hundreds or even more)or pins around the periphery of the chip. Each of these pins on the chipmay communicatively couple to a PCB pad or trace for subsequent couplingto another location either on this same PCB or to another location.

Again, for higher power applications, the windings of the baluntransformer are typically implemented in the prior art using relativelywider tracks. This increase in size is largely because of the need touse higher currents, to support lower input impedances (Z_(in)), and soon. However, this inherently requires that a larger area on the die isdedicated to the balun (given the wider and thicker tracks employed).The efficiency of the balun also reduces when a very wide baluntransformer arrangement is employed; this is largely because the actualwinding of the balun transformer become further and further apartthereby reducing the communicatively coupling between the windings ofthe primary and secondary of the balun transformer. Tightly coupledrelatively thinner tracks (as in a low power balun transformer) offer ahigh degree of operational efficiency, in that, a high degree ofelectromagnetic coupling may be achieved. The further apart the tracksare, then the lower the degree of electromagnetic coupling may beachieved. The use of these relatively wider tracks, as employed withinhigher power applications, inherently results in a component havingwindings that are relatively further apart and therefore have a lowerdegree of electromagnetic coupling between them.

In addition, this problem can be exacerbated when the integrated circuitoperates within a communication device that operates within a wirelesscommunication system.

Looking at one example of a WLAN (Wireless Local Area Network)communication system operating according to one of the IEEE (Instituteof Electrical & Electronics Engineers) 802.11 standards or recommendedpractices whose RF (Radio Frequency) carrier frequency, f, is within the2.4 GHz (Giga-Hertz) frequency range, these relatively large trackwindings employed within such a transformer balun can operate as anantenna with respect to the wireless communication existing therein.This can lead to a great degree of interference.

As can be seen, there are many serious deficiencies when using a priorart approach of wide track balun transformers within integratedcircuits. A great deal of interference and reduction of performance ofthe communication device may be experienced when using these prior artapproaches. Clearly, there is a need in the art for a more effective andefficient way of performing the conversion between differential andsingle-ended signals, particularly within the high power and wirelesscommunication system contexts.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theSeveral Views of the Drawings, the Detailed Description of theInvention, and the claims. Other features and advantages of the presentinvention will become apparent from the following detailed descriptionof the invention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a diagram illustrating a prior art embodiment of a singletransformer balun (having relatively wide tracks) within an integratedcircuit (shown using a side view).

FIG. 1B is a diagram illustrating the same prior art embodiment of asingle transformer balun (having relatively wide tracks) within anintegrated circuit (shown using a top view).

FIG. 2 is a diagram illustrating an embodiment of a WLAN (Wireless LocalArea Network) communication system that may be implemented according tocertain aspects of the invention.

FIG. 3 is a schematic block diagram illustrating a communication systemthat includes a plurality of base stations and/or access points, aplurality of wireless communication devices and a network hardwarecomponent in accordance with certain aspects of the invention.

FIG. 4 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device and an associatedradio in accordance with certain aspects of the invention.

FIG. 5 is a diagram illustrating an embodiment of a communication device(shown in transceiver embodiment) that is built according to theinvention.

FIG. 6 is a diagram illustrating an embodiment of a communication devicesupporting IEEE (Institute of Electrical & Electronics Engineers)802.11b functionality in accordance with certain aspects of theinvention.

FIG. 7 is a diagram illustrating an embodiment of a communication devicesupporting both IEEE 802.11b functionality and Bluetooth® functionalityin accordance with certain aspects of the invention.

FIG. 8 is a diagram illustrating an embodiment of a double transformerbalun that supports maximum PA (Power Amplifier) power in accordancewith certain aspects of the invention.

FIG. 9 is a flowchart illustrating an embodiment of a method forproviding maximum output power from a PA (Power Amplifier) according tocertain aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Communication systems are known to support wireless and wire linedcommunications between wireless and/or wire lined communication devices.Such communication systems range from national and/or internationalcellular telephone systems to the Internet to point-to-point in-homewireless networks, among other communication system types. Each type ofcommunication system is constructed, and hence operates, in accordancewith one or more communication standards and/or protocols. For instance,wireless communication systems may operate in accordance with one ormore standards including, but not limited to, IEEE (Institute ofElectrical & Electronics Engineers) 802.11, Bluetooth® (e.g., the IEEE802.15.1 Bluetooth® core), AMPS (Advanced Mobile Phone Services),digital AMPS, GSM (Global System for Mobile communications), CDMA (CodeDivision Multiple Access), LMDS (Local Multi-point DistributionSystems), MMDS (Multi-channel-Multi-point Distribution Systems), and/orvariations thereof.

Depending on the type of wireless communication system, a wirelesscommunication device, such as a cellular telephone, two-way radio, PDA(Personal Digital Assistant), PC (Personal Computer), laptop computer,home entertainment equipment, et cetera, communicates directly orindirectly with other wireless communication devices. For directcommunications (also known as point-to-point communications), theparticipating wireless communication devices tune their receivers andtransmitters to the same channel or channels (e.g., one of the pluralityof RF (Radio Frequency) carriers of the wireless communication system)and communicate over that channel(s). For indirect wirelesscommunications, each wireless communication device communicates directlywith an associated BS (Base Station) (e.g., for cellular services)and/or an associated AP (Access Point) (e.g., for an in-home orin-building wireless network) via an assigned channel. To complete acommunication connection between the wireless communication devices, theassociated BSs (Base Stations) and/or associated APs communicate witheach other directly, via a system controller, via the PSTN (PublicSwitch Telephone Network), via the Internet, and/or via some other WAN(Wide Area Network).

For each wireless communication device to participate in wirelesscommunications, it includes a built-in radio transceiver (i.e., receiverand transmitter) or is coupled to an associated radio transceiver (e.g.,a station for in-home and/or in-building wireless communicationnetworks, RF modem, etc.). A transmitter of such a communication deviceincludes a data modulation stage, one or more IF (IntermediateFrequency) stages, and a PA (Power Amplifier). The data modulation stageconverts raw data into baseband signals in accordance with a particularwireless communication standard. The one or more IF stages mix thebaseband signals with one or more local oscillations to produce RFsignals. The PA amplifies the RF signals prior to transmission via anantenna.

A receiver of such a communication device is coupled to the antenna andincludes a LNA (Low Noise Amplifier), one or more IF stages, a filteringstage, and a data recovery stage. The LNA receives inbound RF signalsvia the antenna and amplifies them. The one or more IF stages mix theamplified RF signals with one or more local oscillations to convert theamplified RF signal into baseband signals or IF signals. The filteringstage filters the baseband signals or the IF signals to attenuateunwanted out of band signals to produce filtered signals. The datarecovery stage recovers raw data from the filtered signals in accordancewith the particular wireless communication standard.

It is also noted that certain variations of such communication devicesperform frequency conversion directly from carrier frequency (e.g. RFfrequency in some instances) to baseband and vice versa. That is to say,direct conversion of such frequencies may be performed within acommunication device that operates according to certain aspects of theinvention without departing from the scope and spirit of the inventionthereof.

Within these various types of communication systems, there is inherentlya need to communicatively couple the various integrated circuits,modules, and functional blocks therein such that they may operatecooperatively to perform their individual respective operations inconjunction with the other parts of the communication device. Certain ofthese components operate within the high power context (e.g., the PA(Power Amplifier) referred to above in one such component). A novelapproach is presented herein by which a double transformer balun may beimplemented to support for a maximum PA power. The manner by which adifferential signal, provided as an output from a PA core, is convertedto a single-ended signal may be implemented such that impedance, Z,matching may be performed according to the antenna or line that the PAis driving. In addition, the secondary coils of the double transformerbalun can operate as a trap or choke with respect to any RF signalswithin the on-chip signals that are amplified by the PA. These secondarycoils operate to keep out any AC (Alternating Current) signal component,and to pass only the DC (Direct Current) signal component. This canensure that the on-chip supply voltage signal that is provided to thePA, VDD_(PA), is choked out from the signals on which the PA is actuallyoperating.

This novel approach by which a double transformer balun may beimplemented to support for a maximum PA power may be used within any ofa variety of communication devices within a variety of communicationsystems. For example, the functionality of the invention may be found ina variety of communication devices including those that operateaccording to the various standards and recommended practices that areprovided under the umbrella of the IEEE 802.11 working group and/or theWi-Fi Alliance (e.g., including the IEEE 802.11a standard, the IEEE802.11b standard, and the IEEE 802.11g standard). Moreover, thefunctionality of the invention may also be found in communicationdevices that operate according to the wireless Bluetooth® communicationstandard and other wireless standards including the various standardsand recommended practices that are provided under the umbrella of theIEEE (Institute of Electrical & Electronics Engineers) 802.15 workinggroup (e.g., including the IEEE 802.15.1 Bluetooth® core, the IEEE802.15.2 recommended practice specification, the IEEE 802.15.3 high datarate PAN standard, and the IEEE 802.15.3 WPAN (Wireless Personal AreaNetwork) High Rate Alternative PHY Task Group 3a (TG3a) which issometimes referred to the IEEE 802.15.3a extended high data rate PANstandard).

In addition, the functionality of the invention may be implementedwithin a variety of types of communication devices including thoseoperable within various wireline and/or wireless based communicationsystems. This functionality may also be implemented within a monolithicsingle chip design of an integrated circuit that may be employed withina wireless (e.g., IEEE 802.11b and/or Bluetooth®) transceiver or othertype device that is part of a larger communication system. Moreover,this functionality may also be found within a mouse, keyboard, or othertype peripheral type device that is part of a larger computer typesystem in a cable replacement implementation approach such that each ofthese peripheral type devices may be viewed as being a transceiver.

FIG. 2 is a diagram illustrating an embodiment of a WLAN (Wireless LocalArea Network) communication system that may be implemented according tothe invention. The WLAN communication system may be implemented toinclude a number of devices that are all operable to communicate withone another via the WLAN. For example, the various devices that eachinclude the functionality to interface with the WLAN may include any 1or more of a laptop computer, a television, a PC (Personal Computer), apen computer (that may be viewed as being a PDA (Personal DigitalAssistant) in some instances, a personal electronic planner, or similardevice), a mobile unit (that may be viewed as being a telephone, apager, or some other mobile WLAN operable device), and/or a stationaryunit (that may be viewed as a device that typically resides in a singlelocation within the WLAN). The antennae of any of the various WLANinteractive devices may be integrated into the corresponding deviceswithout departing from the scope and spirit of the invention as well.

This illustrated group of devices that may interact with the WLAN is notintended to be an exhaustive list of devices that may interact with aWLAN, and a generic device shown as a WLAN interactive device representsany communication device that includes the functionality in order tointeractive with the WLAN itself and/or the other devices that areassociated with the WLAN. Any one of these devices that associate withthe WLAN may be viewed generically as being a WLAN interactive devicewithout departing from the scope and spirit of the invention. Each ofthe devices and the WLAN interactive device may be viewed as beinglocated at respective nodes of the WLAN.

It is also noted that the WLAN itself may also include functionality toallow interfacing with other networks as well. These external networksmay generically be referred to as WANs (Wide Area Networks). Forexample, the WLAN may include an Internet I/F (interface) that allowsfor interfacing to the Internet itself. This Internet I/F may be viewedas being a base station device for the WLAN that allows any one of theWLAN interactive devices to access the Internet.

It is also noted that the WLAN may also include functionality to allowinterfacing with other networks (e.g., other WANs) besides simply theInternet. For example, the WLAN may include a microwave tower I/F thatallows for interfacing to a microwave tower thereby allowingcommunication with one or more microwave networks. Similar to theInternet I/F described above, the microwave tower I/F may be viewed asbeing a base station device for the WLAN that allows any one of the WLANinteractive devices to access the one or more microwave networks via themicrowave tower.

Moreover, the WLAN may include a satellite earth station I/F that allowsfor interfacing to a satellite earth station thereby allowingcommunication with one or more satellite networks. The satellite earthstation I/F may be viewed as being a base station device for the WLANthat allows any one of the WLAN interactive devices to access the one ormore satellite networks via the satellite earth station I/F.

This finite listing of various network types that may interface to theWLAN is also not intended to be exhaustive. For example, any othernetwork may communicatively couple to the WLAN via an appropriate I/Fthat includes the functionality for any one of the WLAN interactivedevices to access the other network.

Any of the various WLAN interactive devices described within thisembodiment may include an encoder and a decoder to allow bi-directionalcommunication with the other WLAN interactive device and/or the WANs.The encoder of any of these various WLAN interactive devices may beimplemented to encode information (using its corresponding encoder) in amanner in accordance with various communication standards and/orprotocols of the WLAN communication system. Analogously, the decoder ofany of the various WLAN interactive devices may be implemented to decodethe transmitted signal (using its corresponding decoder) in a mannerthat also comports with the various communication standards and/orprotocols of the WLAN communication system. This diagram shows just oneof the many possible communication system embodiment types in whichvarious communication devices may be implemented that can include anyone or more of the various aspects of the invention. Within any one ofthese communication devices, a double transformer balun may beimplemented to support for a maximum PA power for a PA that isimplemented therein.

In some instances, any one of the WLAN interactive devices may becharacterized as being an IEEE 802.11 operable device. For example, suchan 802.11 operable device may be an 802.11a operable device, an 802.11boperable device, an 802.11g operable device, or an 802.11n operabledevice. Sometimes, an IEEE 802.11 operable device is operable tocommunicate according to more than one of the standards (e.g., both802.11a and 802.11g in one instance). The IEEE 802.11g specificationextends the rates for packet transmission in the 2.4 GHz (Giga-Hertz)frequency band. This is achieved by allowing packets, also known asframes, of two distinct types to coexist in this band. Frames utilizingDSSS/CCK (Direct Sequence Spread Spectrum with Complementary CodeKeying) have been specified for transmission in the 2.4 GHz band atrates up to 11 Mbps (Mega-bits per second) as part of the 802.11bstandard. The IEEE 802.11b standard may also operate in the 2.4 GHzspectrum using CSMA/CA (Carrier Sense Multiple Access with CollisionAvoidance) as its media access approach. The 802.11a standard uses adifferent frame format with OFDM (Orthogonal Frequency DivisionMultiplexing) to transmit at rates up to 54 Mbps with carrierfrequencies in the 5 GHz range. The 802.11g specification allows forsuch OFDM frames to coexist with DSSS/CCK frames at 2.4 GHz.

Regardless of which type of communication device and which type ofcommunication system in which a communication device may be implemented,the novel approach by which an integrated circuit may include a doubletransformer balun to support maximum PA power may be used to provide forimproved performance of that particular communication device and theoverall communication system. Various other embodiments are alsodescribed below to show some of the various types of communicationdevices and/or communication systems in which certain aspects of theinvention may be found.

FIG. 3 is a schematic block diagram illustrating a communication systemthat includes a plurality of base stations and/or access points, aplurality of wireless communication devices and a network hardwarecomponent in accordance with certain aspects of the invention. Thewireless communication devices may be laptop host computers, PDA(Personal Digital Assistant) hosts, PC (Personal Computer) hosts and/orcellular telephone hosts. The details of any one of these wirelesscommunication devices is described in greater detail with reference toFIG. 4 below.

The BSs (Base Stations) or APs (Access Points) are operably coupled tothe network hardware via the respective LAN (Local Area Network)connections. The network hardware, which may be a router, switch,bridge, modem, system controller, et cetera, provides a WAN (Wide AreaNetwork) connection for the communication system. Each of the BSs or APshas an associated antenna or antenna array to communicate with thewireless communication devices in its area. Typically, the wirelesscommunication devices register with a particular BS or AP to receiveservices from the communication system. For direct connections (i.e.,point-to-point communications), wireless communication devicescommunicate directly via an allocated channel.

Typically, BSs are used for cellular telephone systems and like-typesystems, while APs are used for in-home or in-building wirelessnetworks. Regardless of the particular type of communication system,each wireless communication device includes a built-in radio and/or iscoupled to a radio. The radio includes a highly linear amplifier and/orprogrammable multi-stage amplifier as disclosed herein to enhanceperformance, reduce costs, reduce size, and/or enhance broadbandapplications.

FIG. 4 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device and an associatedradio in accordance with certain aspects of the invention. For cellulartelephone hosts, the radio is a built-in component. For PDA PDA(Personal Digital Assistant) hosts, laptop hosts, and/or personalcomputer hosts, the radio may be built-in or an externally coupledcomponent.

As illustrated, the host device includes a processing module, memory,radio interface, input interface and output interface. The processingmodule and memory execute the corresponding instructions that aretypically done by the host device. For example, for a cellular telephonehost device, the processing module performs the correspondingcommunication functions in accordance with a particular cellulartelephone standard or protocol.

The radio interface allows data to be received from and sent to theradio. For data received from the radio (e.g., inbound data), the radiointerface provides the data to the processing module for furtherprocessing and/or routing to the output interface. The output interfaceprovides connectivity to an output display device such as a display,monitor, speakers, et cetera, such that the received data may bedisplayed or appropriately used. The radio interface also provides datafrom the processing module to the radio. The processing module mayreceive the outbound data from an input device such as a keyboard,keypad, microphone, et cetera, via the input interface or generate thedata itself. For data received via the input interface, the processingmodule may perform a corresponding host function on the data and/orroute it to the radio via the radio interface.

The radio includes a host interface, a digital receiver processingmodule, an ADC (Analog to Digital Converter), a filtering/gain module,an IF (intermediate Frequency) mixing down conversion stage, a receiverfilter, an LNA (Low Noise Amplifier), a transmitter/receiver switch, alocal oscillation module, memory, a digital transmitter processingmodule, a DAC (Digital to Analog Converter), a filtering/gain module, anIF mixing up conversion stage, a PA (Power Amplifier), a transmitterfilter module, and an antenna. The antenna may be a single antenna thatis shared by the transmit and the receive paths as regulated by theTx/Rx (Transmit/Receive) switch, or may include separate antennas forthe transmit path and receive path. The antenna implementation willdepend on the particular standard to which the wireless communicationdevice is compliant.

The digital receiver processing module and the digital transmitterprocessing module, in combination with operational instructions storedin memory, execute digital receiver functions and digital transmitterfunctions, respectively. The digital receiver functions include, but arenot limited to, digital IF (Intermediate Frequency) to basebandconversion, demodulation, constellation demapping, decoding, and/ordescrambling. The digital transmitter functions include, but are notlimited to, scrambling, encoding, constellation mapping, modulation,and/or digital baseband to IF conversion. The digital receiver andtransmitter processing modules may be implemented using a sharedprocessing device, individual processing devices, or a plurality ofprocessing devices. Such a processing device may be a microprocessor,micro-controller, DSP (Digital Signal Processor), microcomputer, CPU(Central Processing Unit), FPGA (Field Programmable Gate Array),programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on operational instructions. The memorymay be a single memory device or a plurality of memory devices. Such amemory device may be a ROM (Read Only Memory), RAM (Random AccessMemory), volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, and/or any device that stores digital information.It is noted that when either of the digital receiver processing moduleor the digital transmitter processing module implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory storing the corresponding operationalinstructions is embedded with the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.

In operation, the radio receives outbound data from the host device viathe host interface. The host interface routes the outbound data to thedigital transmitter processing module, which processes the outbound datain accordance with a particular wireless communication standard (e.g.,IEEE 802.11, Bluetooth®, et cetera) to produce digital transmissionformatted data. The digital transmission formatted data is a digitalbase-band signal or a digital low IF signal, where the low IF typicallywill be in the frequency range of one hundred kHz (kilo-Hertz) to a fewMHz (Mega-Hertz).

The DAC converts the digital transmission formatted data from thedigital domain to the analog domain. The filtering/gain module filtersand/or adjusts the gain of the analog signal prior to providing it tothe IF mixing stage. The IF mixing stage converts the analog baseband orlow IF signal into an RF signal based on a transmitter local oscillationprovided by local oscillation module. The PA amplifies the RF signal toproduce outbound RF signal, which is filtered by the transmitter filtermodule. The antenna transmits the outbound RF signal to a targeteddevice such as a base station, an access point and/or another wirelesscommunication device.

The radio also receives an inbound RF signal via the antenna, which wastransmitted by a BS, an AP, or another wireless communication device.The antenna provides the inbound RF signal to the receiver filter modulevia the Tx/Rx switch, where the Rx filter bandpass filters the inboundRF signal. The Rx filter provides the filtered RF signal to the LNA,which amplifies the signal to produce an amplified inbound RF signal.The LNA provides the amplified inbound RF signal to the IF mixingmodule, which directly converts the amplified inbound RF signal into aninbound low IF signal or baseband signal based on a receiver localoscillation provided by local oscillation module. The down conversionmodule provides the inbound low IF signal or baseband signal to thefiltering/gain module. The filtering/gain module filters and/or gainsthe inbound low IF signal or the inbound baseband signal to produce afiltered inbound signal.

The ADC converts the filtered inbound signal from the analog domain tothe digital domain to produce digital reception formatted data. Thedigital receiver processing module decodes, descrambles, demaps, and/ordemodulates the digital reception formatted data to recapture inbounddata in accordance with the particular wireless communication standardbeing implemented by radio. The host interface provides the recapturedinbound data to the host device via the radio interface.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 4 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented onone integrated circuit, the digital receiver processing module, thedigital transmitter processing module and memory may be implemented on asecond integrated circuit, and the remaining components of the radio,less the antenna, may be implemented on a third integrated circuit. Asan alternate example, the radio may be implemented on a singleintegrated circuit. As yet another example, the processing module of thehost device and the digital receiver and transmitter processing modulesmay be a common processing device implemented on a single integratedcircuit. Further, the memories of the host device and the radio may alsobe implemented on a single integrated circuit and/or on the sameintegrated circuit as the common processing modules of processing moduleof the host device and the digital receiver and transmitter processingmodule of the radio.

An integrated circuit within the wireless communication device of FIG. 4that includes the PA may be implemented such that the interface betweenthe PA and the Tx filter module and subsequently to the antenna that thePA is driving may be implemented using a double transformer balun thatsupports maximum PA power. That is to say, a conversion from adifferential signal, output from the PA, to the antenna that the PA isdriving may be implemented using a double transformer balun that isimplemented to support a maximum PA power as presented and describedherein.

FIG. 5 is a diagram illustrating an embodiment of a communication devicethat is built according to the invention. This embodiment shows acommunication system that is capable of being implemented within awireless type communication system; however, such a communication devicecould alternatively be implemented within a wireline type communicationsystem as well without departing from the scope and spirit of theinvention.

Being shown in a wireless context, this embodiment of a communicationdevice includes an antenna that is operable to communicate with any 1 ormore other communication devices within a given communication network.An antenna interface communicatively couples a signal to be transmittedfrom the communication device or a signal received by the communicationdevice to the appropriate path (be it the transmit path or the receivepath).

A radio/analog front end (that may also be referred to as “radio frontend,” “analog front end,” “radio,” and/or “front end”) includes bothreceiver functionality and transmitter functionality. The radio frontend communicatively couples to an analog/digital conversion functionalblock. The radio front end communicatively couples to amodulator/demodulator, and the radio front end communicatively couplesto a channel encoder/decoder.

Along the Receive Path:

The receiver functionality of the radio/analog front end includes a LNA(Low Noise Amplifier)/filter. The LNA/filter is followed by a mixer thatis operable to perform any modification in frequency of the receivedsignal. Using the mixer, the receiver functionality of the front endperforms any down-converting that may be required from a carrierfrequency by which the received signal was transmitted. This may beperformed by converting first down to an IF (Intermediate Frequency), orit may alternatively include down-converting directly from the receivedsignal to a baseband signal (e.g. a direct conversion process). Inaddition, the mixer is followed by a BPF (Band Pass Filter) that isoperable to tune the tuning frequency of the radio/analog front end tothe appropriate frequency and therefore the appropriate channel.

Whichever particular manner is employed, a baseband signal is outputfrom the receiver functionality of the radio/analog front end and isprovided to an ADC (Analog to Digital Converter) that samples thatsignal and outputs the digital I, Q (In-phase, Quadrature) components ofthe baseband signal.

These I, Q components are provided to a demodulator portion of themodulator/demodulator where any modulation decoding/symbol mapping isperformed such that the digitally sampled received symbol is mapped toan appropriate modulation (that includes a constellation andcorresponding mapping). Examples of such modulations may include BPSK(Binary Phase Shift Key), QPSK (Quadrature Phase Shift Key), 8 PSK (8Phase Shift Key), 16 QAM (16 Quadrature Amplitude Modulation), and evenother modulation types including higher order modulation types. Theappropriately mapped symbols are then provided to a decoder portion ofthe channel encoder/decoder where best estimates of the information bitscontained within the received symbols are made.

Along the Transmit Path:

Somewhat analogous and opposite processing is performed in the transmitpath when compared to the receive path. Information bits that are to betransmitted are encoded using an encoder of the channel encoder/decoder.These encoded bits are provided to a modulator of themodulator/demodulator where modulation encoding/symbol mapping may beperformed according to the modulation of interest. These now I, Qcomponents of the symbols are then passed to a DAC (Digital to AnalogConverter) of the analog/digital conversion functional block. The nowanalog signal to be transmitted is then passed to a transmit driver thatperforms any necessary up-converting/modification to the analog signalto comport it to the communication channel over which the signal is tobe transmitted to another communication device via the antenna. Thistransmit driver may be implemented using a PA as also described abovewith respect to other embodiments. The chip that includes the PA may beimplemented and mounted on a PCB, and the interface between the PA andthe antenna that the PA is driving may be implemented using a doubletransformer balun that supports maximum PA power. That is to say, aconversion from a differential signal, output from the PA, to theantenna that the PA is driving may be implemented using a doubletransformer balun that is implemented to support a maximum PA power aspresented and described herein.

FIG. 6 is a diagram illustrating an embodiment of a communication devicesupporting IEEE (Institute of Electrical & Electronics Engineers)802.11b functionality in accordance with certain aspects of theinvention. This diagram shows how IEEE 802.11b WLAN functionality may beimplemented on a small, single-sided module that can be optimized forhandheld applications. The following diagram (FIG. 7) shows how anoptional Bluetooth® populate option on a second side of the board forusers who may want an extremely broad range of operations andcommunication systems types in which the communication device mayoperate and thereby providing an extremely versatile range in wirelessconnectivity.

Referring to the FIG. 6, an IEEE 802.11b functional block may beimplemented as a monolithic, single chip. A dual antenna approach may beemployed for diversity in dealing with undesirable deleterious effectssuch as multi-path effects. A diversity antenna switch may be used toselect either one or both of the 2 antennae of the communication device.A Tx/Rx switch coupled to the diversity antenna switch determineswhether to be transferred to the receive or transmit paths of thecommunication device. The receive path includes a balun whose output isthen communicatively coupled to the radio. The transmit path, extendingfrom the radio, communicatively couples to a balun, then to a PA (PowerAmplifier) whose output is communicatively coupled off-chip to a BPF(Band Pass Filter) using a double transformer balun that is implementedto support a maximum PA power, and then back through the Tx/Rx switch.

As mentioned above, this IEEE 802.11b functional block can be employedas a single chip IEEE 802.11b implementation. An extremely efficientmeans of integration is performed to include a radio, an IEEE 802.11bbaseband processor, a MAC (Medium Access Controller), a PA (PowerAmplifier), and all other RF (Radio Frequency) components that wouldtypically be found on a LAN (Local Area Network) circuit board. However,all of these components can now be provided within a single integratedcircuit (e.g., a single chip). The radio may be implemented to performdirect conversion of a signal from a carrier frequency to a basebandsignal. For example, the radio may be implemented to perform directconversion of a 2.4 GHz signal to a baseband signal using componentshaving an all CMOS (Complementary Metal Oxide Semiconductor) design.This all-CMOS implementation of the radio provides for a significantdecrease in power consumption and a reduction in many, many componentsthereby providing for improved power management (e.g., power reduction)and also thereby providing for a more affordable communication devicethat can perform wireless connectivity. Such a communication devicehaving this implementation can have an extended battery life due to thelow power all-CMOS design and the comprehensive power managementperformed therein. The comprehensive power management approach canimprove the battery life by creating a deep sleep state when thecommunication device is in a stand-by mode. Some of the high performanceand interfacing features of this communication device include SDIO(Secure Digital Input/Output), SDIO with a Bluetooth® option, SPI(Serial Peripheral Interface), CF (Compact Flash), and PCMCIA (PersonalComputer Miniature Communications Interface Adapter).

FIG. 7 is a diagram illustrating an embodiment of a communication devicesupporting both IEEE 802.11b functionality and Bluetooth® functionalityin accordance with certain aspects of the invention. This embodimentshows a coexistence I/F (interface) between an IEEE 802.11b functionalblock and a Bluetooth® functional block. Each of these two functionalblocks may be individual chips. Together, these chipsets cooperativelycan provide for IEEE 802.11b functionality and Bluetooth® functionality.This combination of these two separate functional blocks effectivelyaddresses the size, power, cost, interface, manufacturing, and ease ofdeployment issues necessary for a solution targeted at the handheldwireless market.

This coexistence may be implemented in a very compact wireless device bymounting the IEEE 802.11b functional block as an integrated circuit onone side of a PCB, and the Bluetooth® functional block as anotherintegrated circuit on the other side of the very same PCB. Thiscoexistence interface between the WLAN (e.g., IEEE 802.11b) and theBluetooth® chipsets ensures an optimal simultaneous performance of bothof the wireless communication protocols.

FIG. 8 is a diagram illustrating an embodiment of a double transformerbalun that supports maximum PA (Power Amplifier) power in accordancewith certain aspects of the invention. This diagram shows, morespecifically, the manner in which the interface between a PA core and anantenna or line that the PA is driving may be performed using a doubletransformer balun design that allows for maximum power to be derivedfrom the PA. The PA core itself may be implemented using 2 MOSFET (MetalOxide Semiconductor Field Effect Transistor) types devices that operateon differential types signals. The nodes corresponding to the supplypotential level and ground potential levels within the chip (e.g.,within the “package”) and at the nodes of the PA core are shown asVDD_(PA) and GND_(PA), respectively. The output signal from the PA coreis shown as being a differential signal. As mentioned above, the use ofdifferential signals may be employed for a variety of improvedperformance considerations including noise immunity. The differentialoutput signal, from the PA core, is provided to a double transformerbalun that is implemented according to certain aspects the inventionsuch that an off-chip single-ended signal may be provided to an antennaand/or line to which the chip is communicatively coupled. The antennaand/or line to which the chip is communicatively coupled is shown ashaving a characteristic impedance. The double transformer balun includesa functional block that operates to match this characteristic impedanceof the antenna and/or line.

The double transformer balun includes a double transformer functionalblock that includes 2 separate transformers that are connectedappropriately to provide for the function and benefits of certainaspects of the invention. The connections of the 2 separate transformersmay be viewed as being a simple, parallel connection. One leg of thedifferential signal output from the PA core (e.g., output from one ofthe MOSFET components of the PA core) is provided simultaneously to bothends of the secondary winding of the double transformer balun (e.g.,shown pictorially as the top and bottom of the secondary winding of thedouble transformer balun). The other leg of the differential signaloutput from the PA core (e.g., output from the other MOSFET component ofthe PA core) is provided to the node at which the windings of thesecondary windings of each of the 2 transformers that compose the doubletransformer are communicatively coupled. That is to say, the secondarywindings of each of the 2 transformers that compose the doubletransformer are communicatively coupled together: the output from one ofthe MOSFET devices of the PA core is provided to this node, and theother output from the other of the MOSFET devices of the PA core isprovided to the other ends of each of the 2 transformers that composethe double transformer.

The primary windings of the double transformer are connected in such away that the primary windings of each of the 2 transformers that composethe double transformer are communicatively coupled at a node; the groundpotential level voltage is effectively coupled to this node. The otherends of each of the windings of the primary windings of each of the 2transformers that compose the double transformer are alsocommunicatively coupled to one another. Similarly, the windings of thesecondary windings of each of the 2 transformers that compose the doubletransformer are communicatively coupled at a node; the VDD_(PA) levelsignal is effectively coupled to this node. The other ends of each ofthe windings of the secondary windings of each of the 2 transformersthat compose the double transformer are also communicatively coupled toone another. This may be viewed as a parallel connected doubletransformer arrangement.

An on-chip single-ended is thereby output from the double transformerfunctional block of the double transformer balun. This on-chipsingle-ended signal is provided to a matching Z (impedance) block thatincludes a matching capacitor, C_(m), in some embodiments.

From certain perspectives, the matching Z block may be viewed asincluding a capacitor whose capacitive-reactance

$\left( {Z_{C_{m}} = {{{- j} \cdot \left( \frac{1}{\omega \; C_{m}} \right)} = {{- j} \cdot \left( \frac{1}{2\pi \; {f \cdot C_{m}}} \right)}}} \right)$

substantially cancels the inductive-reactance, (Z_(antenna)=jωL=j2ωfL),that is associated with the antenna (or line) at a predeterminedoperating frequency, f. For example, at the predetermined operatingfrequency, f, the value of C_(m) is selected such that the values ofZ_(c) _(m) , and Z_(antenna) are substantially equal in magnitude andopposite in sign.

Moreover, the matching Z block may include the appropriate impedance tomatch the Z of the antenna or line to which the integrated circuit iscommunicatively coupled and that the PA is driving. This matching Zblock may include any combination of Rs, Ls, and/or Cs (resistors,inductors, and/or capacitors) as necessary to provide a Z such that ismatches the Z of the antenna or line to which the integrated circuit iscommunicatively coupled and that the PA is driving. In some embodiments,the RF (Radio Frequency) carrier frequency, f, at which thecommunication system including this integrated circuit generates acharacteristic impedance of an antenna (e.g., as in a wirelesscommunication system context) of approximately 50Ω (that is primarilyinductive-reactance). In such instances, the characteristic impedance ofthe matching Z block is also designed to be approximately 50Ω (however,implemented primarily as capacitive-reactance, which is opposite in signto the antenna's primarily inductive-reactance). In these instances, thecharacteristic impedance of the antenna is typically not totallyresistive in nature, and the matching Z block ensures that anappropriate amount of inductor-related impedance and/orcapacitor-related impedance (e.g., sometimes referred to asinductive-reactance and/or capacitive-reactance) is included to matchsubstantially the characteristic impedance of the antenna.

It can be seen that the double transformer balun, as described herein,includes both the double transformer and the matching Z block. Thedouble transformer balun approach presented herein is a significantdeparture from the prior art approaches to use a single transformerbalun with relatively wider tracks in an effort to support high powerapplications on-chip. The double transformer balun approach presentedherein provides for a component that is operable to support high powerapplications requiring higher currents. This approach also provides forrelatively low input impedance, Z_(in), as seen by the PA core whenproviding its differential signal.

By using the double transformer design of the double transformer balunapproach presented herein, thinner tracks can be employed therebyensuring a high degree of electromagnetic coupling between the primaryand secondary windings of the double transformer. These windings may beimplemented using a standard CMOS (Complementary Metal OxideSemiconductor) process (e.g., using approximately 12 μm (micro-meter)thickness tracks). That is to say, each of the primary windings and thesecondary windings of each of the two separate transformers of thedouble transformer may be implemented using on the integrated circuitthat includes the double transformer balun using tracks that aregenerated using a standard CMOS process that generated tracks having awidth of approximately 12 μm.

This is in contrast to the prior art approach or using wider tracks(e.g., thicker metal) to fabricate the windings of a single transformerbalun; this prior art approach to employing a single transformer balunis typically not a practical approach. For higher power applications,the width of the tracks of a single transformer balun needs to be sorelatively wide (to support the higher currents) that theelectromagnetic coupling of the transformer is significantlycompromised. This also results in a significant reduction in the powerefficiency of the single balun transformer. The double transformerapproach of the double transformer balun described herein has greaterperformance and improved efficiency than the prior art approaches ofusing wider tracks with a single transformer balun.

It is also noted that the secondary coils of the double transformerbalun also operate as a choke for the on-chip PA supply voltage,VDD_(PA). The secondary coils can operate as an RF (Radio Frequency)trap or choke to keep any AC (Alternating Current) signal components andto pass any DC (Direct Current) components. Also, the primary coils canoperate as RF chokes or traps as well with respect to the differentialinput signal that is received by the double transformer of the doubletransformer balun.

It is also noted that the double transformer balun may be implementedusing the processing and techniques described according to a symmetricalon-chip balun as described in the following U.S. utility patentapplication/U.S. patent:

1. U.S. Utility patent application Ser. No. 10/055,425, entitled“ON-CHIP TRANSFORMER BALUN,” (Attorney Docket No. BP2095), filed Jan.23, 2002, now issued as U.S. Pat. No. 6,801,114 on Oct. 5, 2004.

FIG. 9 is a flowchart illustrating an embodiment of a method forproviding maximum output power from a PA (Power Amplifier) according tocertain aspects of the invention. The method involves receiving adifferential signal from a PA (Power Amplifier) core. The method theninvolves converting the differential signal received from the PA core toan on-chip single-ended signal using a double transformer of a doubletransformer balun. The method then involves passing the on-chipsingle-ended signal through a matching Z (impedance) block of the doubletransformer balun. The impedance of the matching Z block substantiallymatches characteristic impedance of antenna or line communicativelycoupled to chip (that is driven by PA). The method then involvesoutputting an off-chip single-ended signal from the matching Z block ofthe double transformer balun.

It is also noted that various methods may be performed, in accordancewith the invention, in a manner similar to the operation andfunctionality of the various system and/or apparatus embodimentsdescribed above. In addition, such methods may be viewed as beingperformed within any of the appropriate system and/or apparatusembodiments (communication systems, communication transmitters,communication receivers, communication transceivers, and/orfunctionality described therein) that are described above withoutdeparting from the scope and spirit of the invention.

Various aspects of the invention can be found in a double transformerbalun that is implemented in an integrated circuit. The doubletransformer balun includes a double transformer and a matching impedanceblock. The double transformer s operably coupled to convert adifferential signal to an on-chip single-ended signal. The doubletransformer includes two separate transformers communicatively coupledin a parallel manner. The matching impedance block is operably coupledto each of primary windings of the two separate transformers of thedouble transformer to provide impedance matching for an antenna and/or aline that is communicatively coupled to an output of the matchingimpedance block. The on-chip single-ended signal passes through thematching impedance block before being provided off-chip via the outputof the matching impedance block.

In certain embodiments, the differential signal is received from a PA(Power Amplifier) core that is also implemented on the integratedcircuit, and the differential signal is provided to each of secondarywindings of the two separate transformers of the double transformer. ThePA core may be implemented on the integrated circuit using a firstMOSFET (Metal Oxide Semiconductor Field Effect Transistor) device and asecond MOSFET device such that a first leg of the differential signal isselected from the first MOSFET device and a second leg of thedifferential signal is selected from the second MOSFET device. Thematching impedance block may be implemented to include a capacitorhaving a capacitive-reactance that substantially cancels aninductive-reactance associated with at least one of the antenna and theline at a predetermined operating frequency. Alternatively, anyappropriate combination of elements may be employed to ensure that acharacteristic impedance of the matching impedance block substantiallymatches the characteristic impedance of the antenna and/or line that thePA is driving.

The secondary windings of the two separate transformers of the doubletransformer may be viewed as operating as RF (Radio Frequency) chokesthat substantially block any AC (Alternating Current) signal componentfor the differential signal. Analogously, the primary windings of thetwo separate transformers of the double transformer may be viewed asoperating as RF chokes that substantially block any AC signal componentfor the on-chip single-ended signal.

The two separate transformers of the double transformer arecommunicatively coupled in a parallel manner such that the primarywindings of the two separate transformers are connected at a first nodeand at a second node, respectively. The on-chip single-ended signal isprovided from the first node to the matching impedance block, and thesecond node is communicatively coupled to an on-chip PA supply voltage.In addition, the two separate transformers of the double transformer arecommunicatively coupled in a parallel manner such that each end ofsecondary windings of the two separate transformers are connected at athird node and at a fourth node, respectively, and the second node iscommunicatively coupled to an on-chip PA supply voltage and also iscenter-tapped to each end of the secondary windings of the two separatetransformers.

The primary windings and secondary windings of each of the two separatetransformers of the double transformer may be implemented on theintegrated circuit using tracks generated by a CMOS (Complementary MetalOxide Semiconductor) process of approximately 12 μm (micro-meter)thickness. The integrated circuit may be implemented within a widevariety of communication devices includes a communication device thatsupports wireless communication according to at least one of an IEEE(Institute of Electrical & Electronics Engineers) 802.11b standard andan IEEE 802.15.1 Bluetooth® core.

The invention envisions any type of communication device that supportsthe functionality and/or processing described herein. Moreover, varioustypes of methods may be performed to support the functionality describedherein without departing from the scope and spirit of the invention aswell.

In view of the above detailed description of the invention andassociated drawings, other modifications and variations will now becomeapparent. It should also be apparent that such other modifications andvariations may be effected without departing from the spirit and scopeof the invention.

1. An apparatus, comprising: a double transformer including a firsttransformer, having a first primary winding and a first secondarywinding, and a second transformer, having a second primary winding and asecond secondary winding, wherein: a first end of the first secondarywinding and a first end of the second secondary winding connected forreceiving a first leg of a differential signal; a second end of thefirst secondary winding and a second end of the second secondary windingconnected for receiving a second leg of the differential signal; a firstend of the first primary winding and a first end of the second primarywinding connected for outputting a single-ended signal; and a second endof the first primary winding and a second end of the second primarywinding grounded.
 2. The apparatus of claim 1, wherein: a first centertap of the first secondary winding and a second center tap of the secondsecondary winding connected to a power supply.
 3. The apparatus of claim1, wherein: the single-ended signal being generated within the doubletransformer based on the differential signal.
 4. The apparatus of claim1, further comprising: an impedance having an input for receiving thesingle-ended signal from the double transformer and having an output forproviding an off-chip single-ended signal to at least one of an antennaand a line; and wherein: the impedance effectuating impedance matchingwith the at least one of an antenna and a line.
 5. The apparatus ofclaim 4, wherein: the impedance including a capacitor having acapacitive-reactance for substantially canceling an inductive-reactanceassociated with at least one of the antenna and the line at apredetermined operating frequency.
 6. The apparatus of claim 1, wherein:the double transformer implemented within an integrated circuit.
 7. Theapparatus of claim 1, further comprising: a power amplifier (PA) corefor providing the differential signal to the double transformer; animpedance having an input for receiving the single-ended signal from thedouble transformer and having an output for providing an off-chipsingle-ended signal to at least one of an antenna and a line; andwherein: the impedance effectuating impedance matching with the at leastone of an antenna and a line; the PA, the double transformer, and theimpedance implemented within an integrated circuit.
 8. The apparatus ofclaim 1, wherein: windings of each of the first transformer and thesecond transformer of the double transformer implemented on anintegrated circuit using tracks generated by a CMOS (Complementary MetalOxide Semiconductor) process of approximately 12 μm (micro-meter)thickness.
 9. The apparatus of claim 1, wherein: each of the firstsecondary winding and the second secondary winding operative as an RF(Radio Frequency) choke for substantially blocking any AC (AlternatingCurrent) signal component for the differential signal.
 10. The apparatusof claim 1, wherein: each of the first primary winding and the secondprimary winding operative as an RF (Radio Frequency) choke forsubstantially blocking any AC (Alternating Current) signal component forthe on-chip single-ended signal.
 11. The apparatus of claim 1, wherein:the apparatus being a communication device operative in accordance withat least one wireless communication standard or protocol.
 12. Anapparatus, comprising: a power amplifier (PA) core for providing adifferential signal; a double transformer including a first transformer,having a first primary winding and a first secondary winding, and asecond transformer, having a second primary winding and a secondsecondary winding, wherein: a first end of the first secondary windingand a first end of the second secondary winding connected for receivinga first leg of the differential signal; a second end of the firstsecondary winding and a second end of the second secondary windingconnected for receiving a second leg of the differential signal; a firstend of the first primary winding and a first end of the second primarywinding connected for outputting a single-ended signal; a second end ofthe first primary winding and a second end of the second primary windinggrounded; and a first center tap of the first secondary winding and asecond center tap of the second secondary winding connected to a powersupply; and an impedance having an input for receiving the single-endedsignal from the double transformer and having an output for providing anoff-chip single-ended signal to at least one of an antenna and a line.13. The apparatus of claim 12, wherein: the impedance effectuatingimpedance matching with the at least one of an antenna and a line; andthe impedance including a capacitor having a capacitive-reactance forsubstantially canceling an inductive-reactance associated with at leastone of the antenna and the line at a predetermined operating frequency.14. The apparatus of claim 12, wherein: the PA, the double transformer,and the impedance implemented within an integrated circuit.
 15. Theapparatus of claim 12, wherein: windings of each of the firsttransformer and the second transformer of the double transformerimplemented on an integrated circuit using tracks generated by a CMOS(Complementary Metal Oxide Semiconductor) process of approximately 12 μm(micro-meter) thickness.
 16. The apparatus of claim 12, wherein: theapparatus being a communication device operative in accordance with atleast one wireless communication standard or protocol.
 17. A method foroperating a communication device, the method comprising: employing adouble transformer for receiving a differential signal, wherein thedouble transformer including a first transformer, having a first primarywinding and a first secondary winding, and a second transformer, havinga second primary winding and a second secondary winding, including: at afirst end of the first secondary winding connected to a first end of thesecond secondary winding, receiving a first leg of the differentialsignal; at a second end of the first secondary winding connected to asecond end of the second secondary winding, receiving a second leg ofthe differential signal; from a first end of the first primary windingconnected to a first end of the second primary winding, outputting asingle-ended signal as a second end of the first primary winding and asecond end of the second primary winding grounded.
 18. The method ofclaim 17, further comprising: receiving the differential signal from apower amplifier (PA) core; employing an impedance having an input forreceiving the single-ended signal from the double transformer and havingan output for providing an off-chip single-ended signal to at least oneof an antenna and a line; and wherein: the impedance effectuatingimpedance matching with the at least one of an antenna and a line; thePA, the double transformer, and the impedance implemented within anintegrated circuit of the communication device.
 19. The method of claim17, wherein: windings of each of the first transformer and the secondtransformer of the double transformer implemented on an integratedcircuit using tracks generated by a CMOS (Complementary Metal OxideSemiconductor) process of approximately 12 μm (micro-meter) thickness.20. The method of claim 17, wherein: the communication device operativein accordance with at least one wireless communication standard orprotocol.